Fluid flow conduit vibrator and method

Abstract

Vibrations are created in a flow conduit by constraining a bluff object having a plurality of positions between which flow of fluid forces the bluff object. In a preferred embodiment, the vibration technique is utilized in a gravel packing tool. Gravel pack sand is placed while the gravel pack tool is vibrated by balls constrained within a wash pipe. A considerably improved gravel pack density is achieved.

We claim: 
     
       1. A gravel packing apparatus for placing a gravel pack within a portion of a wellbore comprising: a) a fluid flow path comprising a work string within which a slurry comprising a carrier fluid and gravel pack solids can be transported to near the portion of the wellbore within which the gravel pack is to be placed, a cross over tool capable of directing slurry flow from the drill string to the portion of the wellbore to be packed, a screen defining a sand free volume within the wellbore through which the carrier fluid but not the gravel pack solids can pass into the same free volume from the portion of the wellbore to be packed, and a means to direct the carrier fluid from the sand free volume to the wellbore above the portion of the wellbore to be gravel packed; and   b) within the fluid flow path, a vibrator constrained within the fluid flow path comprising a movable bluff hammer capable of moving between a plurality of positions wherein fluid flow through the fluid flow path causes the bluff hammer to move between positions and change direction of the movement of the bluff hammer after the bluff hammer impacts a wall of the fluid flow path.   
     
     
       2. The gravel packing apparatus of claim 1 wherein the means to direct the carrier fluid from the sand free volume to the wellbore comprises a wash pipe. 
     
     
       3. The gravel packing apparatus of claim 2 wherein the vibrator is contained in the wash pipe. 
     
     
       4. The gravel packing apparatus of claim 3 wherein the wash pipe contains a plurality of vibrators. 
     
     
       5. The gravel packing apparatus of claim 1 wherein the hammer is an essentially round ball. 
     
     
       6. The gravel packing apparatus of claim 5 wherein the movement of the essentially round ball is constrained by perforated upstream plates and perforated downstream plates. 
     
     
       7. The gravel packing apparatus of claim 6 wherein the means to direct the carrier fluid from the sand free volume to the wellbore comprises a washpipe, and the vibrator is contained within the wash pipe. 
     
     
       8. The gravel packing apparatus of claim 1 wherein the movement of the hammer is constrained by an anchor rod affixed to the hammer at one end and pivotably affixed at the other end to the apparatus. 
     
     
       9. The gravel packing apparatus of claim 1 wherein the hammer is constrained by a flexible cable affixed to the hammer at one end and affixed at the other end to a stationary position within the fluid flow path. 
     
     
       10. The gravel packing apparatus of claim 1 wherein the vibrator is contained in the crossover tool.